Given the ever-increasing demand for high-speed data services, modern wireless networks will increasingly require more efficient strategies for use of the available frequency spectrum, which is likely to be among the key rate-limiting factors for effectively meeting this increased demand. One key limit to spectrum utilization efficiency involves the current practice of half duplex RF communication, in which a node either transmits or receives a signal in a single channel usage. Furthermore, communication is often asymmetrical and is becoming more so over time. From the view point of traffic symmetry between uplink (mobile to base-station) and downlink (base-station to mobile), data traffic started as highly symmetrical with voice services. Over time, however, it has become markedly imbalanced, with the major growth of new multimedia services being characterized by asymmetric traffic (much higher downlink). Overall traffic patterns are also becoming more asymmetrical because the largest bandwidth demand currently derives from downstream TV and Internet video signals.
It is therefore desired to increase the spectrum efficiency of such RF systems. Full duplex, in which a node can transmit and receive on the same frequency at the same time, is also desirable. However, transmitting a high-power signal from the same station that is receiving a low-power signal increases self-interference, making it difficult to distinguish the low-power signal from noise or from the high-power signal.
RFID backscatter modulation has been used to permit the same antenna to transmit data using a received un-modulated carrier. However, RFID is generally limited to low-power operation and is generally only half-duplex.
There is, therefore, a need of an improved way of performing data communications.